The present invention relates to an ophthalmic surgical instrument with components facilitating clocked orientation of a surgical tip to its outer shell/handle, and components facilitating dimensionally-accurate manufacture including defect-free welding.
Ophthalmic surgical instruments are highly refined medical tools used in eye surgery, such as for cataract lens extraction. Such products are commercially manufactured and available, such as from Alcon company, including for example the Infinity® Vision System and/or Ozil® Vision System. It is important that the surgical instrument that contacts the patient and that is handled by the surgeon be of the highest quality, since the human eye is a delicate organ and the surgical procedure is very delicate. Therefore, reliability, durability, safety, ease of use, ease of sterilization, and numerous other aspects of the surgical instrument and related methods are very important. Also, physicians demand high quality and appealing aesthetics. At the same time, cost and manufacturability is important.
One tip used with hand-held ophthalmic surgical instruments is a replaceable tip, such as a phaco tip, with a straight end with beveled tip end, or a slightly bent/curved end with oriented tip end. Surgeons prefer that the bent/beveled end have a particular orientation relative to the handle when the surgeon picks up the instrument, so that the surgeon does not have to look to see the orientation of the bent/beveled end. In other words, surgeons want to intuitively known which way the bent/beveled end is “facing” when they pick up the instrument based on feel. The relative rotational orientation of parts is referred to herein as “clocking”. Threaded connections provide an inconsistent angular rotational position (i.e. inconsistent “clocking”), particularly when torqued to a desired preload. Preloading is a requirement for these tips, since the instruments sonically vibrate the tips during use, and a significant torsional preload is required to prevent unacceptable risk of loosening during use. Depending on the design, the instrument may have multiple threaded connections for supporting the tip (e.g. a tip threaded into a horn, and also the horn threaded into a support shaft and/or to the handle/shell). Multiple threaded connections further amplify the problem of inconsistent “clocking” of the bent/beveled end to the instrument's handle/shell. Specifically, the combination of the threads, the preloads, and tolerance stack-up of the multiple components of the instruments makes it difficult to predict exactly what direction a bent/beveled end may face in a fully assembled instrument, thus resulting in an unacceptable number of bent/beveled tip ends being oriented outside a preferred angular range.
Some existing manufacturing processes and instrument designs attempt to deal with this clocking problem by replacing one or more of the threaded connection(s) with a press-fit arrangement, where the final clocked rotational position of the bent/beveled end (and/or of interconnected components affecting clocking of the bent/beveled end) is set by a press-fit process. However, press-fit assembly processes do not provide a strength, robustness, and durability of threaded connections. Further, the tips must be replaceable, which press-fit does not support. Still further, standard existing tips include threaded connections, so it is difficult to eliminate the use of threads, since the industry presently uses them. Nonetheless, it is potentially a significant advantage to provide features and/or characteristics that result in components pre-set at the factory to have a particular clocked orientation when assembled, such as at a supplier's site, rather than requiring this be done at the overall system equipment manufacturer/assembler.
The handset in the present ophthalmic surgical instrument includes several components made of titanium that are fixedly connected by welding. Though titanium is a preferred material for the present handset, titanium is difficult to weld in a defect-free manner. At the same time, surgical handsets must be made defect-free so as to avoid any cracks, crevices, or imperfections that might harbor germs and unwanted organics and contaminants. Notably, defects in handsets can cause an increase in sterilization time and/or frustrate optimal sterilization. Also, defective handsets can have appearance issues causing surgeons to object to or misinterpret the handset's quality.
In addition to high standards for defect-free handsets, ophthalmic handsets also have high standards for dimensional consistency and accuracy. Further, the handsets must be light in weight to facilitate easy and non-tiring use by the surgeon. Also, it is preferable that the handsets use a minimum of materials to reduce manufacturing cost. This leads to a dilemma where the handset's outer shell must preferably be thin-walled, yet thin walls can cause secondary problems. For example, some instrument designs require a thin-walled outer shell (such as an extruded thin-walled outer shell) welded to a machined tip. However, it is difficult to weld onto thin walls without distortion (due to the heat required for good welding, and/or issues related to non-uniform heating and later cooling), thus leading to welding defects and/or dimensional defects, especially near the weld area.
Thus, improvements are desired that positively affect each, any and all of the above items.